This application is to support the next phase (Phase III) of the Diabetes Control and Complications Trial (DCCT). The Children's Hospital of Philadelphia/University of Pennsylvania is one of 21 centers participating in this national collaborative trial. The aim of the DCCT is to examine the question which has bedeviled researchers in diabetes since the discovery of insulin: in a randomized prospective study will management of patients with Type I diabetes on a regimen which produces normal to near-normal levels of blood glucose be associated with a rate of diabetic complications (especially ophthalmic, neurologic and renal) which is equal to, greater than, or less than that seen in a control group? And what is the cost of such an intensive program, in terms of side effects, actual fiscal expenditures and emotional impact? Funds are requested for a full scale clinical trial. Our Center was successful in achieving the goals for Phase II and now is prepared and committed to enter Phase III. Phase III will permit the continued follow-up of the patients already recruited and randomized into the study, plus the recruitment, screening, randomization and follow-up of new patients to a total of 55 participants. Recruitment, screening, and treatment will be done according to the DCCT Protocol and the DCCT Manual of Operations.